Oxygenate-to-olefin conversion reactions typically involve contacting an oxygenate feedstock with a formulated molecular sieve catalyst. As the reaction proceeds, coke (a carbonaceous material) builds up on the molecular sieve catalyst. This coke is removed by passing the catalyst through a regenerator.
During the conversion reaction the molecular sieve serves as a catalyst and therefore is not directly consumed by the oxygenate conversion reaction. The molecular sieve, however, can become damaged or degraded for a variety of reasons. Damaged or degraded molecular sieve is less effective at catalyzing an oxygenate-to-olefin reaction. Due to the cost of replacing degraded catalyst, reducing or eliminating degradation of molecular sieve within an oxygenate-to-olefin reaction system is desirable.
U.S. Patent Application Publication 2006/0040821 (Pujado) describes a method for performing an oxygenate-to-olefin reaction. In Pujado, methods are provided for removing metal salts from the gas stream fed to a regenerator.
U.S. Pat. No. 7,479,468 (van Egmond et al.) describes incorporation of an air separation unit into an oxygenate-to-olefin reaction system. In van Egmond et al., one use for the streams produced by the air separation unit can be as a regeneration medium for regeneration of coked catalyst.
What is desired are methods that allow for more efficient conversion of oxygenates to olefins. In particular, methods are desired that allow for protection of catalyst used in such conversions during periods of extended use.